1. Field of the Invention
This invention relates generally to mooring systems for offshore structures such as platforms and vessels and in particular, to a device which supports the mooring chain in such systems.
2. Description of the Prior Art
FIG. 1 illustrates a prior art mooring line connector illustrated in U.S. Pat. No. 6,663,320. This known connector allows the mooring line to rotate in two perpendicular planes relative to the offshore structure to which it is attached. The mooring line is connected using a rod and a latch mechanism. Adjustment of the length of the mooring line, which is often desired before and sometimes after installation of the mooring line, disadvantageously must take place before the rod is connected, most likely on board of another vessel.
FIG. 2 illustrates a prior art mooring line connector from UK Patent Application GB2351058. The chain stopper provides two axes of rotation, advantageously providing reduced chain wear, but it is not designed to minimize so called out-of-plain bending, which occurs when the chain is under tension and one chain link (the captive link) is fixed by the chain stopper while the adjacent link below the captive link is allowed to rotate relative to the captive link. Also, during chain installation and tensioning, an uplift force is produced in the connector that must be resolved by bending the line of chain or by other means.
3. Identification of Objects of the Invention
A primary object of this invention is to provide a chain support in which fatigue damage due to out-of-plane bending is reduced.
Another object of this invention is to provide a chain support that allows rotation about two perpendicular axes whereby the maximum total rotation about the first axis is at least 90 degrees and the rotation about the second axis is ±15 degrees.
Another object of this invention is to provide a chain support that allows the upper end of the mooring line to be pulled up vertically through the assembly while at the same time allowing large vertical angle variations of the lower end of the mooring, without inducing objectionable vertical or lateral misalignment of the assembly with the mooring line.
Another object of this invention is to provide a chain support that allows adjustment of the mooring line length at any time by pulling in or letting out chain links with the capability of latching into every other chain link.
Another object of this invention is to provide a chain support with an arrangement of components that minimizes the overall width of the assembly.